The invention relates to a physiologically operational, rate-adaptive cardiac pacemaker.
Such cardiac pacemakers are for example known from U.S. Pat. No. 4,140,132 and European Patent Application No. 0 080 348. The described cardiac pacemaker comprises an activity sensor which detects the intensity of movement of the patient. An evaluation circuit measures the output signal of a bending vibrator and evaluates the spectral peaks which are created by an activity of the patient above a defined programmable predeterminable threshold. The basic pacing rate of the cardiac pacemaker is varied in accordance with these detected activity levels which change together with each activity of the patient and--in the case of a demand pacemaker--the escape sequences of the pacemaker are also varied between the predetermined minimum and maximum values.
The known cardiac pacemakers have the disadvantage that the rate of change of the stimulation rate is only dependent on the number of the signals received which characterize the activity of the patient and do not provide any information about the signal intensity. For example, when the patient moves by walking, only the step speed `ut not the step intensity can be measured, so that the difference between an exhausting jog with a larger step length and a walk at the same step speed but with a smaller step length cannot be determined.